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Our system involves…the intake and

digestion of food, absorption of nutrients, and elimination of solid waste.

What is our system?

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Gastro-Intestinal System

Alexandra Ford, Jenna Volpe, Alexa Mastriano and Alexis

Tomaszewski

Functions of the GI System

Digestion

Produces various chemicals to break down food molecules

Filters out harmful substances

Removes solid waste

What is Digestion?

The chemical breakdown of complex biological molecules into their component parts

The breakdown involves… Lipids – Fatty Acids Proteins – Amino Acids Carbohydrates- Simple Sugars

5 Stages of Digestion

1. Ingestion2. Movement3. Mechanical and Chemical

Digestion4. Absorption5. Elimination

Two Different Types of Digestion….

Mechanical Digestion

Chemical Digestion

What do you think the difference is?

Mechanical Digestion

Changes the physical form of food

EXAMPLES Chewing Tearing Grinding Mashing Mixing

Chemical Digestion

Changes the chemical composition of food with the aid of digestive enzymes

EXAMPLES Carbohydrates Proteins Lipids

GI Tract

Parts of the GI Tract

– Tube within a tube– Direct link/path between organs

Structures• Pharynx• Esophagus• Stomach• Small intestine• Large Intestine• Rectum

Pharynx

Connects the nasal and oral cavities with the larynx and esophagus

There are 3 parts to the pharynx:o nasopharynxo oropharynxo laryngopharynx

Parts of the Pharynx

Nasopharynxo provides a passageway for air when breathing

Oropharynxo passageway for food to move from the mouth,

and for air to move to and from the nasal cavity

Laryngopharynxo provides a passageway to the esophagus

Esophagus

Approximately 10” long

Functions include:

1. Secrete mucus

2. Moves food from the throat to the stomach using muscle movement called peristalsis

If acid from the stomach gets in here that’s heartburn.

Stomach

J-shaped muscular bag that stores the food you eat, breaks it down into tiny pieces.

Mixes food with digestive juices that contain enzymes to break down proteins and lipids.

Acid in the stomach kills bacteria.

Food found in the stomach is called chyme.

Stomach

The stomach is divided into the fundus (upper, rounded

part), body (main portion), and antrum (lower part).

Rugae- the folds in the mucosa lining the stomach.

Gastric Secretions: Thick mucus membrane forms the inner lining of stomach ,

studded with small openings (gastric pits) that are at the ends of gastric glands

-Gastric glands have 3 types of secretory cells; mucous, chief, and parietal

cells

o Chief secrete digestive enzymes

o Parietal release hydrochloric acid

o The digestive enzymes and the hydrochloric acid forms gastric juice.

Small Intestine

Small intestines are roughly 7 meters long

Lining of intestine walls has finger-like projections called villi, to increase surface area.

The villi are covered in microvilli which further increases surface area for absorption.

Small Intestine

Digestion in Small Intestine Produces:

1) disaccharides

2) fatty acids

3) peptidesmonoglycerides

Portions of the Small Intestine:

1) duodenum

2) jejunum

3) ileum

Small Intestine

Nutrients from the food pass into the bloodstream through the small intestine walls.

Absorbs: 80% ingested water Vitamins Minerals Carbohydrates Proteins Lipids

• Secretes digestive enzymes

Large Intestine

About 5 feet long

Accepts what small intestines don’t absorb

Rectum (short term storage which holds feces before it is expelled).

Large Intestine

Functions Bacterial digestion

Ferment carbohydrates Protein breakdown

Absorbs more water Concentrate wastes

Large Intestine

Movement

• Slower than in the small intestine. Peristaltic waves happen 2-3 times a day. Intestinal wall constricts vigorously and forces the intestinal contents toward the rectum.

• Defecation reflex: holding a deep breath and contracting the abdominal wall muscles increases internal abdominal pressure and forces feces into the rectum.

Feces from the Large Intestine

Feces

• Materials that were not absorbed or digested, and water (75%), electrolytes, mucus, and bacteria.

• Odor is from a variety of compounds that bacteria produces.

• Color is from pigments now altered by bacterialß action.

Accessory Organs

Include: Liver, gall bladder, and pancreas

Not part of the path of food, but play a critical role.

Liver

Directly affects digestion by producing bile Bile helps digest

fat filters out toxins

and waste including drugs and alcohol

Liver Functions

Carbohydrate metabolism- helps maintain concentration of blood glucose

Lipid metabolism-oxidizes fatty acids at a high rate, synthesizing lipoproteins, phospholipids, and cholesterol, and converting portions of carbohydrate and protein molecules into fat molecules

Protein metabolism-deaminated amino acids, synthesizing plasma proteins, and converting certain amino acids to other amino acids

Gall Bladder

Stores bile from the liver, releases it into the small intestine.

Fatty diets can cause gallstones

Gall Bladder Functions

Stores bile between meals, reabsorbs water to concentrate bile, and contracts to release bile into small intestine

Functions of Bile Salts

-Aid digestive enzymes

-Break down fat globules into smaller droplets (emulsification)

-Then they mix with water so the fat molecules can be digested more effectively

Pancreas

Produces digestive enzymes to digest fats, carbohydrates and proteins

Regulates blood sugar by producing insulin

Pancreas

Pancreatic Juice- Contains enzymes that digest carbohydrates, fats, nucleic acids, and proteins

Pancreatic amylase -splits molecules of starch or glycogen into double sugars

Pancreatic lipase- breaks triglyceride molecules to fatty acids and glycerol

-Two nucleases, which are enzymes, break down nucleic acid molecules into nucleotides

-Trypsin, chymotrypsin, and carboxypeptidase (protein splitting enzymes) split the bonds between certain amino acids in proteins

Oral Cavity

Mouth

Teeth mechanically break down food into small pieces. Tongue mixes food with saliva (contains amylase, which helps break down starch).

Epiglottis is a flap-like structure at the back of the throat that closes over the trachea preventing food from entering it.

Salivary Glands

2 types of secretory cells:o serous cells: produce a watery fluid that is rich

in proteins and glycoproteins as well as amylase (split starch and glycogen molecules into disaccharides)

o mucous cells: secrete a thick mucus which lubricates the food before it is swallowed

Salivation: occurs when one prepares to eat, and nerve signals activate salivary glands to moisten the mouth

The amount of saliva secreted depends on how appealing the particular food is to the individual

Three Types of Salivary Glands

Salivary Glands

partoids large secrete 25% of saliva (watery) front of ears extending to jaw bone (1 on each

side) drains into mouth near upper teeth

submandibular secrete 70% of saliva (mucus) drains into mouth from under tongue

sublingual smallest secrete 5% of saliva (mucus) drains into floor of mouth

Lips and Cheeks

LIPS sensory receptors and provide information

about food before its in the mouth few differences between lips and skin on

bodyo no sebaceous glands- keep moisturized with

salivao no hair follicles

Cheeks

Does anyone remember the scientific name for cheeks?

-stratified squamous epithelium

-inside of cheek is lined by mucous membrane

Tongue

guides and molds food in the mouth

composed of skeletal muscle fibers (willingly controlled)

mucous membrane protects it from microbes and pathogens

lingual frenulum connects tongue to floor of mouth

perceives taste and texture

over 10,000 taste buds (change with age)

Palate

o forms the roof of the oral cavity and consists of a bony anterior part and a muscular posterior part

o palatine tonsils- two lymphatic tissue masses, located on either side of the pharynxo help protect the body against infection

(respiratory)

Fun Facts

HOW LONG ARE YOUR INTESTINES? At least 25 feet in an adult. Be glad you're not a full-grown horse -- their coiled-up intestines are 89 feet long!

Food drying up and hanging out in the large intestine can last 18 hours to 2 days!

In your lifetime, your digestive system may handle about 50 tons!!

On a sheet of paper, write the name of each colored organ:

Green:

Red:

Pink:

Brown:

Purple:

Green:

Yellow:

How’d you do?

Green: Esophagus

Red: Stomach

Pink: Small Intestine

Brown: Large Intestine

Purple: Liver

Green: Gall Bladder

Yellow: Pancreas